Credit 3 Extra Flashcards
Describe ventricular tachycardia and it’s ECG changes
Impulses are repetitively generated from one or more ventricular foci.
Ventricular tachycardias differ in morphology, rate, regularity, and duration.
The P waves are normal, have no fixed relationship to wide and bizzare QRS complexes.
- They occur before, during, or after the QRS complex, but have no fixed relationship = P wave differ from beat to beat.
Ventricular tachycardias can be:
- Uniform: All QRS complexes are of one, there is one focus from which all QRS complexes originate
- Multiform: Called multifocal. There are different sites of origin
What is typical for multifocal premature ventricular complexes?
For example from lead II
- a single premature ventricular beat occurs
- then two normal beats.
- and finally 3 premature beats in a row.
When these 3 premature beats occur in succession it is called a run and now having a different configuration, meaning morphology is different.
Describe ventricular fibrillation and it’s ECG changes
Characteristic are rapid irregular, unorganized deflections on the ECG.
Changes on the ECG:
- P waves, QRS complexes, and T waves are not detectable.
There are continuous positive and negative oscillations that are chaotic and bizzare activity of heart.
Coarse fibrillation – a deflection of high amplitude than fine fibrillation has.
A terminal rhytm resulting in NO ventricular contractions causing cardiac arrest.
Triggers may be
- myocardial ischaemia, hypothermia and drugs
Define and characterize right bundle branch block
Characteristics:
A delay in conduction to the right ventricle leading to that the right ventricle will continue to be depolarized.
Changes on the ECG tracings:
- Decrease the size of the R wave in leads I,II, III and AVF
- Large and wide S waves in leads I,II,III and aVF
- Cause of a prolonged conduction time the QRS complex is wider than normal
Define and characterize left bunde branch block
Characteristics:
Delayed depolarization of the left ventricle
Changes on the ECG tracings:
- Wider QRS complex
- An increase in the R wave height in the lead II
- The T wave is large and opposite in polarity to the QRS complex
Mechanism of development of myopathies caused by ischaemic imbalances
Downer Cow syndrome
Also called
- Maternal obstetric paralysis
- Obturator paralysis
Occurs often in the first 2 - 3 days after calving, in heavy milk producers.
Characterized by
- Inability to stand
- Affected hindlimbs are commonly directed behind the cow in a frog-leg attitude.
Due to:
- Unsifficient blood supply to affected areas of muscles causing them to undero athropy and later necrosis
- Traumatic injuries: during parturition due to slipping or forced to stand up too quick
- Difficult parturition due to eg. an oversized calf
What are typical for AV blocks?
Characteristics:
The normal sequence of cardiac activation includes slowed conduction through the AV node, allowing sequential activation of the atria and then ventricles.
Conditions:
enhanced vagal tone, drugs, structural diseases of the AV node
Altered intraatrial conduction + altered conduction in both bundle branches simultaneously result in
Classified into:
First-, second-, and third degree AV blocks
Describe Premature atrial complexes
Occurs when an ectopic site depolarizes at a rate faster than the sinus node.
Rare in dogs and cats but can be associated with
- Atrial enlargement
- Acid/base or electrolyte abnormalities
- Hypoxia
Causes changes on ECG;
- A normal appearing QRS complex but that occurs too early (premature)
- An abnormal P wave
- P - P duration is highly variable depending on origin of the ectopic impulse
Describe sinus arrhytmia
The rhytm originate from the sinus node but the rhytm is irregular
Defined as rhytmic speeding and slowing of the rhythm so that the variability of the R-R interal is greater than 10%
A wandering pacemaker; P wave is varying in shape and is biphasic or will reverse its polarity.
A chaning heart rate accompanied by shifting the pacemaker site within the SA node and / or atrium
What is respiratory sinus arrhytmia?
When the sinus arrhytmia is linked to the respiratory cycle, when the rate increase with inspiration and slows on expiration
Describe sinus block
When the impulse is blocked before exciting the SA node
What are the types of abnormalities in impulse conduction (conduction disturbances)?
- Atrioventricular blocks (AV blocks)
- Bundle branch blocks
